Guiding Light

Happy Friday! Today on Museum Bites we’re touring Valley Camp, a massive Great Lakes freighter that has been transformed into a maritime museum. Located in Sault Sainte Marie, Michigan, Valley Camp (formerly known as the Louis W. Hill) was launched in 1917 and for 49 years hauled cars, coal, grain, and iron ore. Today it is filled with a wide variety of seafaring gizmos and gadgets, including a stunning collection of Fresnel lenses. Join me for a closer look at this ingenious device.

Valley Camp Museum Ship, Photo by cjverb (2019)-1
Valley Camp Museum Ship, Photo by cjverb (2019)

Blinded by the Light:  In 1822, French physicist and optics pioneer, Augustin-Jean Fresnel (1788-1827) debuted his first lens. Made of thick glass, with a lamp at its center, this ridged contraption is not only a technical wonder it is a dazzling work of art. When lit, the lens refracts the light and concentrates the rays into a powerful beam.

Fresnel’s device rocked the maritime world. Prior to his invention, lighthouses used mirrors to reflect light and enhance illumination. The result was weak, could only be detected from short distances, and could rarely be seen during fog or stormy weather. Fresnel’s lens more than doubled the current level of illumination. Within a few years, he increased the number of lenses to his original design which produced multiple rotating beams from a single source of light. This new and improved Fresnel lens kicked out a beam that could be seen 20+ miles away.  If you’d like to geek out on the technical aspects of Fresnel lenses, click on this HyperPhysics link, courtesy of the Department of Physics and Astronomy at Georgia State University.

Fun Fresnel Fact: After receiving his degree in engineering, Fresnel went to work for the French government. However, in 1815 he lost his job when Napoleon Bonaparte returned to power after his exile on Elba. Fresnel used the yearlong hiatus to conduct experiments, particularly in the area of optics. Despite being rehired by the French government after the Second Restoration, Fresnel continued his optics research.

1st-Order Fresnel Lens, Key West Lighthouse Museum, Photo by Acroterion, Wikimedia Commons
1st-Order Fresnel Lens, Key West Lighthouse Museum, Photo by Acroterion, Wikimedia Commons

Pecking Order:  Fresnel lenses are categorized according to their power and scope, and maritime lenses range from First to Sixth Order. First-Order Fresnel lenses are the largest and most powerful. With a height of 12 or more feet and a range of 20+ miles, these massive lights are used in lighthouses. The wee Sixth-Order Fresnel lens is approximately 17 inches in height and has a range up to 5 nautical miles. These smallest of the regular Fresnel orders are used on piers, jetties and secondary harbors.

Valley Camp has a delightful variety of Fresnel lenses. This stunning Fourth-Order Fresnel lens (see below) on display at Valley Camp is ~28 inches high and has a range of up to 15 nautical miles. Viewed from the outside this brilliant lamp appears to have dual oblong bulbs, but peek inside and a small round light kicks out a hearty glow. The Fourth-Order Fresnel lens is commonly used on the Great Lakes.

Here are more Fresnel lenses from the Valley Camp collection. Unfortunately, not all were labeled, but we can enjoy their dazzling display all the same…

The Fresnel lens has been adapted for use in a variety of devices and used not only to illuminate, but also magnify, project images, and even collect solar energy. You can find them in solar panels, stage lights, projection TVs, as well as the slightly dated overhead projector.

Fun Lighthouse Fact: Pharos of Alexandria is the oldest lighthouse on record. Designed by Sostratus of Cnidus in c270 BCE, this 350-foot tower was built to help ancient Egyptian sailors navigate Alexandria’s tricky harbor. Pharos of Alexandria is one of the seven ancient Wonders of the World and the prototype for all subsequent lighthouses.

That concludes our look at Fresnel lenses. I’ll be back with more treasures from Valley Camp in September. In the meantime, I hope you enjoy these final weeks of summer!

Lightouse, Photo by Evgeni Tcherkasski, Pixabay-cropped-2-100px Cover photo by Evgeni Tcherkasski, courtesy of Pixabay.

Sources:

Britannica: Augustin-Jean Fresnel

Britannica: Fresnel Lens

Britannica: Lighthouse

Britannica: Lighthouse of Alexandria

Florida State University: Fresnel

How Stuff Works: Fresnel Lens

HyperPhysics

National Park Service: Fresnel Lens

Pixabay

Sault Saint Marie Historic Sites: Valley Camp

Wikimedia Commons

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